Crum gives a fascinatingly detailed look at the life of a veterinarian in the second of her series after Cutter. When Santa Cruz, Calif., vet Gail McCarthy shows up to treat Cindy Whitney's gelding, she finds the woman and her husband murdered and a homeless man nicknamed ""the Walker"" running from the scene. After summoning the police and telling them the little she knew about the Whitneys, Gail thinks her part in the investigation is over, although the gossip around town about her finding the couple has just begun. When she is shot at in an obvious ambush after being called out on an emergency one subsequent night, she doesn't immediately connect the incident with the Whitneys' murders. But to be on the safe side, she begins to probe for information about the dead couple and the mysterious Walker and uncovers a coke ring that might involve a detective on the murder case. Top-heavy with interesting horse lore which nearly eclipses it mystery, the story is redeemed by Gail's bright personality and Crum's illuminating conclusion. (Jan.)